A known on-board evaporative emission control system includes a fuel vapor collection canister, which collects volatile fuel vapors from the headspace of the fuel tank, and a canister purge solenoid (CPS) valve for periodically purging collected vapors to an intake manifold of the engine. The CPS valve comprises a solenoid actuator that is under the control of a microprocessor-based engine management system.
Fuel vapors from the tank flow through the vapor line and is stored in the vapor canister. The vapor canister is a storage medium for the hydrocarbon fuel vapors and is filled with carbon which has a natural affinity for hydrocarbons. During vehicle operation, atmospheric air is drawn in through the canister vent and the hydrocarbon vapors are introduced into the engine intake manifold and are mixed with the fuel-air mixture and are burnt in the engine
A known CPS valve includes a movable valve element that is resiliently biased by a compression spring against a valve seat to close the valve to flow when no electric current is being delivered to the solenoid. As electric current is increasingly applied to the solenoid, an increasing electromagnetic force acts in a sense tending to unseat the valve element and thereby open the valve to fluid flow. This electromagnetic force must overcome various forces acting on the mechanical mechanism to unseat the valve element, including overcoming the opposing spring bias force.
Thus, in a know CPS valve, the solenoid must provide sufficient actuating force not only to open the valve, but also to overcome the opposing spring bias force. Further, the solenoid acts against the force of the flow through the valve, which must also be overcome.
Accordingly, a need exists for further improvement in certain aspects of CPS valves.